1. Field of the Invention
The present invention relates to a vehicle suspension, and more particularly, to a walking beam suspension used to position and control axle movement for a trailer.
2. Discussion of Related Art
A conventional vehicle includes a vehicle frame having a pair of longitudinally extending frame rails that support the vehicle engine and body. The frame is supported on a plurality of ground-engaging wheels that are disposed at opposite ends of a plurality of axles. The vehicle may contain, for example, a steer axle on which the wheels are steerable by the vehicle operator, a drive axle whose wheels are driven by the vehicle engine, and one or more non-driven trailer axles. Each of the axles are coupled to the vehicle frame through a suspension that dampens movements transmitted between the wheels and the vehicle frame.
One conventional tandem axle suspension is a walking beam suspension. In a walking beam suspension, a walking beam is located on either side of the vehicle extending longitudinally with respect to the vehicle. Each walking beam is coupled to forward and rear axles of a tandem axle proximate the forward and rear ends, respectively, of the walking beam. The walking beams are also pivotally mounted to the vehicle frame at a location intermediate the forward and rear axles. Although the walking beam may be rigidly attached to the axles using, for example, U-bolts, a more common walking beam suspension has a pivotal bushing connection of the walking beam to the axle and requires a secondary suspension linkage in addition to the walking beam to form a parallelogram linkage geometry for controlling axle jounce and rebound motion. Conventional walking beam suspensions also typically include a single spring disposed between each walking beam and vehicle frame.
Conventional walking beam suspensions have several drawbacks. When the walking beam is rigidly attached to the axles, the use of U-bolts and other means of connecting the walking beams to the axles of the vehicle increase the cost and weight of the suspension. In the more typical walking beam suspension in which the walking beam is pivotally connected to the axles, the requirement for a secondary linkage to control axle movement increases the cost and weight of the suspension. The walking beams in conventional suspensions also suffer undesirable stress from absorbing spring loads in the suspension due to bending loads in the walking beam. The walking beam pivot point inputs a concentrated load into the vehicle frame due to the typical single spring location per side for two axles.
The inventors herein have recognized a need for a vehicle suspension that will minimize and/or eliminate the above-identified deficiencies.